1. Field of the Invention
The subject invention is directed to control moment gyroscopes for providing directional control in a spacecraft, and more particularly, to a system and method for distributing power to an array of control moment gyroscopes.
2. Description of Related Art
Control moment gyroscopes are well known means of providing directional control of spacecraft. One example is described in U.S. Pat. No. 5,386,783 to Havenhill, the disclosure of which is incorporated herein by reference in its entirety. Control moment gyroscopes typically include a rotor, a motor to spin the rotor about a rotor axis, a gimbal, a gimbal torque motor to rotate the gimbal about a gimbal axis and a control system. The control moment gyroscope is mounted within the spacecraft along the axis in which it will induce a torque. The rotor is mechanically supported in the gimbal and is rotated about the gimbal axis, which is normal to the rotor axis.
During operation of the gyroscope, the rotor is spun about its rotor axis by a motor at a predetermined rate. In order to induce a torque on the spacecraft, the gimbal torque motor rotates the gimbal and spinning rotor about the gimbal axis. The rotor is of sufficient mass and is spinning at such a rate that any movement of the rotor out of its plane of rotation will induce a significant torque around an output axis, which is normal to both the rotor axis and the gimbal axis. Torque around the output axis is transferred directly to the spacecraft through a support structure.
In a prior art system, spacecraft bus power is used to spin the rotor and to rotate the gimbal. This power is stored in a battery that is typically charged by solar radiation during periods of spacecraft quiescence. While the rotor is continuously spinning at a predetermined nominal speed and the spin motor is consuming power at constant rate, power to the gimbal torque motor is provided only upon demand. At such a time, the peak power demand can be substantially greater than the normal duty cycle, placing a high demand on spacecraft bus power. It would be beneficial to power a gimbal torque motor without calling upon the spacecraft's bus power. The subject invention provides such a solution, and several other advantages over the prior art, which will become readily apparent from the following detailed description of the invention.